Hi Just to be very clear about this issue:
Your room temperature “moves” at a rate dimensioned in degrees / hour (like 2 degrees / hour) and the period should be out in the half hour to couple of hours range. Put another way, it’s a 1,800 to > 5,000 second sort of thing. Operating with typical loop parameters, a TBolt is locked to GPS past a few hundred seconds. The OCXO simply follows whatever the GPS happens to suggest is correct. The temperature effects (whatever the source) are past the GPS cutover point. Unless you are running the TBolt into something other than an OCXO, the loop will take out *any* of the temperature impacts on the output of the device. That’s just the way a control loop works. It’s how it was designed to work. It also is (most likely) why none of this bothered the original design team. In holdover, you will see / do see / can see the impact of temperature. The gotcha there is that the TBolt has a temperature sensor on it. In holdover that sensor “corrects” the EFC voltage. To the degree this process works, it takes out any temperature impact in holdover. Again, it’s probably why the original design team felt things were ok. So, why when you change this or that (like to a different OCXO) does the temperature sensitivity plot change? Well, if the DAC / reference is the source of the error *and* you reduce the sensitivity of the OCXO, the temperature impact *is* reduced. Go to something like a normal 10811 with a 1x10^7 etc range and the impact should go down by more than an order of magnitude. LH is *not* lying to you….. What is a problem: You look at the plot on LH and conclude that the TBolt is wandering around with temperature changes. That’s not what it’s telling you. The only thing LH *can* observe with just a TBolt are variations that have been corrected for by the control loop. If the loop does not correct for them, the DAC does not change, and LH has nothing to go on. With no data to indicate a change, LH reports that nothing has happened. Again it’s not lying to you. It simply can only do just so much with the information it has. None of this is to say that the various effects are un-interesting. They are fun to watch. What would be more interesting would be to be able to dig a bit deeper. We already can go a lot further into a TBolt than any of the other commercial units. Complaining that we can’t go further is … well … this is TimeNuts …. Bob > On Apr 6, 2018, at 8:30 AM, ew via time-nuts <time-nuts@febo.com> wrote: > > How did you measure temperature sensitivity > Bert Kehren > > In a message dated 4/6/2018 3:40:18 AM Eastern Standard Time, > hol...@hotmail.com writes: > > > I replaced the OCXO on one of my Thunderbolts with an Oscilloquartz 8663 and > the temperature sensitivity went down by about 2/3, so I always assumed the > main contributor was the OCXO. I didn't try mod-ing any other Tbolts. > > I also tried temperature stabilizing the power supply and it seemed to also > have an influence. > > ----------------- > >> I respectfully disagree. The OCXO is not the temperature problem with the >> Tbolt. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.